People often pick up Perfumes, the Guide as a starter into getting more seriously involved on perfume. There are also those who are already into the aficion and check to see whether the snark or the praise corresponds with their own established views. For all practical purposes there are a few editions of the exact same entertaininh and informative book with minimal differences depending on when they came out which makes for some confusion, at least going by the questions appearing on perfume discussion boards. Let's see the various editions according to continent and chronological order of coming out.
First edition of Perfumes, the Guide (2008): Hardcover, blue Dawamesk/Coque d'Or bottle by Guerlain on the white book jacket.
Second edition of Perfumes, the Guide, also called Perfumes, the A-Z Guide: Paperback, contains the exact same content of the first edition, with added reviews that had previously appeared on the three Supplements that had been available through subscription at the authors' site (the first one of those was free for download) and an extention of the essays, with some updates on the "best of" lists at the end of the book.
There are two versions of the 2nd edition of Perfumes, the Guide: One for the US market, another for the European one, but they share the same content as described above.
the US 2nd edition of Perfumes, the Guide with many little bottles in colour on the cover
the European 2nd edition of Perfumes, the Guide, in black & white stripes on the cover
The above are NOT to be confused with the newest upcoming edition, reprising some material from the other book, called "The Little Book of Perfumes: the 100 Classics", which basically takes Luca and Tania on a hunt to re-smell the 100 classic fragrances they had reviewed to see (and wittily comment, of course) whether they stand up to closer scrutiny after the lapsed 3 years and perfumery changes since.